Composing Within a Pentatonic Constraint
A student must compose a 16-bar piece for the school's marimba ensemble, which has instruments tuned to a five-note scale (the equivalent of C, D, F, G, A). The brief says the piece must have a clear call-and-response section, a rhythmic ostinato in the lower instruments, and a contrasting middle section. The student's first draft uses all twelve chromatic notes, has no repeated pattern, and the melody and accompaniment play the same rhythm throughout. The teacher says the draft 'ignores the instruments and the brief'. The student has two lessons to revise before the assessed performance.
1. Explain why the first draft fails the brief, referring to the instruments and the required features.
Read the worked answer
The draft uses twelve chromatic notes, but the marimbas are tuned to only five pitches (C, D, F, G, A). Notes outside that set cannot be played on these instruments, so the draft is unplayable as written. The brief also requires a call-and-response section, but the draft has no alternation between a leading phrase and a answering phrase. It requires a rhythmic ostinato in the lower instruments, but the draft has no repeated pattern. Finally, melody and accompaniment share the same rhythm throughout, so there is no contrast between layers; the required contrasting middle section is also missing. The draft therefore fails on instrumentation, texture, structure and the specific features named in the brief.
2. Give a concrete revision plan for the 16 bars that meets every requirement.
Read the worked answer
Bars 1–8 (call-and-response): the upper marimba plays a two-bar call using only C, D, F, G, A; the lower instruments answer with a two-bar response; repeat this four times. Bars 1–16 (ostinato): the lowest instruments repeat a one-bar rhythmic pattern (e.g., crotchet, two quavers, crotchet) throughout, giving a steady pulse. Bars 9–12 (contrast): change the texture by having the melody play longer notes while the ostinato continues, or move the call to a lower instrument and the response to the upper one, and change the dynamic. Bars 13–16: return to the opening call-and-response material to close the piece. Check every pitch against the five available notes, and make sure the melody's rhythm differs from the ostinato so the layers are distinct.